Manufacture of structural board from



Patented Aug. 11, 1959 MANUFACTURE OF STRUCTURAL BOARD FRGM RUB ENHarland H. Young, Western Springs, and John L. ()hlson and GustaveBarshefsky, Chicago, 111., assignors to Swift & Company, Chicago, 111.,a corporation of Illinois No Drawing. Application September 24, 1953Serial No. 382,186

12 Claims. (Cl. 162-148) The present invention relates generally to anew structural board and the manufacture thereof. More specifically, thepresent invention is directed to a structural board made from abacterially treated material.

Many commercial wall boards have been manufactured from various fibrousraw materials including wood, straw, bagasse, waste paper, and the like.Processes de veloped successfully utilize waste lumber, paper, and thelike, which are in scrap form and therefore considered to be of littlevalue. In such processes a similarity is present in'that the severalsteps which are taken are the same with only slight variationsirrespective of the starting material utilized. The processes arenormally begun with a step in which the basic raw material iscomminuted. The only differences which may arise during the comminutionstep reside in the equipment utilized inasmuch as the nature of the rawmaterial may require different types of equipment. For example, roughwood is usually first passed through a hog or chipper and thereby iscomminuted into the desired starting size. Paper or paper-like material,when sterilized, is sometimes shredded or carded by suitable machinery.In many ways, but for the same purpose and with similar results, thevarious starting materials are comminuted to the correct size for thesubsequent manufacture of a structural board having high strength perunit of weight so that it may be used structurally under circumstanceswhere strength is required.

Following comminution, the basic raw material is subjected to a cookingor chemical treatment. This treatment is used normally to partiallyhydrolyze a portion of the cellulose fibers or lignocellulose materialso that this portion may serve as a binder in the finished board.Another important function of this step is to remove the solubleimpurities which are capable of imparting to the finished boardundesirable properties. If the material is subjected to cooking,pressure cookers are normally utilized. By pressure-cooking thematerial, it is properly conditioned for subsequent treatment, and anyraw material odors present are considerably reduced. One wellknownprocess comprises high-pressure steam cooking, followed by a suddenrelease of the steam pressure, there by effecting defibration andpartial hydrolysis of the material.

In utilizing chemical treatment there are certain chemicals which arecommonly known to be capable of bringing about the reduction of the rawmaterial to fibers. Such chemicals are also utilized to catalyzedesirable hydrolysis. Still other chemicals may be added to bring aboutdeodorization and bleaching effects. One Wellknown and commonly usedpiece of machinery called the Asplund defibrator combines steaming andmechanical defibration. The chemicals which may be used along with theconditions under which proper cooking is obtained are all well known andare quite conventional.

Subsequent to the cooking or chemical treatment of the comminuted rawmaterial, the resultant fibers are refined so as to separate fiberbundles into smaller bundles or individual fibers and forming therewitha slurry or suspension of these fibers. Various well-known methods ofcomminution are utilized in the refining step. This comminution iscarried out in such a manner so as to alleviate excessive destruction ofthe fiber length. Such refining is normally effected by various types ofmechanical working. Well-known machines, such as the Jordan, Bauer,Hollander, or Niagara beaters or mills are of the type utilized as pulpbeaters or pulp formers. This type of machine mills the fibers in watersuspension so as to produce dilute suspensions or slurries of pulpsuitable for felting.

Prior to the felting of the stock it is sometimes desirable toincorporate binders or other chemical additives therewith. Among thesechemical additives are various thermosetting resins, starch,water-proofing materials, fire-proofing materials, and various insectand vermin repellents or poisons. Examples of the Water-proofingmaterials which may be utilized are petrolatum, oils, Waxes, and metalresinates. The fire-proofing materials may include sulphonates,phosphates, and the like. The types of additives aforementioned are usedin order to produce a board of desired characteristics. For example,some sort of binder is necessary in order to hold the fibers in anorientated manner, while water-proofing materials are obviously neededwhen such structural boards are utilized in out-door constructions.Along this same line, the fire-proofing materials are necessities whichprovide a board of much greater utility. In the same category,protection from various insects and vermin is quite often considerednecessary depending upon the various uses of the structural board.

The conventional felting step follows and is accomplished by placing apredetermined amount of pulp slurry, containing the desired additives,in a properly shaped container having a screened surface. Free Water isdrained off, either by gravity or by the utilization of a vacuum, andthe dewatered fibers are collected in the form of a felt on the screen.The free water remaining in the felt is then usually removed ascompletely as possible by pressure rolls. This latter step may beaccelerated by the use of a vacuum. v

Upon preparation of the felts, the next step which is necessary in orderto produce a structural board is the hot pressing of the felts undersufiicient temperatures and pressures to produce a finished board. Theformed felt may first be cold-pressed to remove free water, or may godirectly to the hot-pressing operation. Hot pressing is ordinarilycarried out at temperatures of from 300 to 600 F. and at pressures offrom 300 to 2000 pounds per square inch. In hot-pres sing a wet mat offibers it is customary to use a wire screen on the surface of one pressplate to provide means for the escape of free water during the initialpressing stage and, after this, to provide means for the escape of steamgenerated by the vaporization of the remaining moisture. This hotpressing treatment effectively removes all of the moisture and also setsthe resin or other thermosetting binder. Various pressing cycles may beused depending upon such factors as temperature; pressure; use of none,one, or two screens; freeness of felt; degree of hydration of certainfibers; nature and amount of resin or other binder; and density orhardness desired. Pressures may vary widely during the pressing cycledepending upon the amount of breathing required to release steam fromthe press. Ariotner variant which also determines the amount of pressureto be utilized is the desired density of the final board.

The structural board is substantially completed upon the cold and hotpressing of the felts. Certain finishing operations are necessary inorder to produce the most desirable board. Such operations includetrimming and humidification. The boards may also be tempered o'r sizedafter removal from the press if superior Water resistance is desired.Usually, the sizing operation is carried out prior to the felting of thefibers. The common sequence followed in carrying out these operationsinvolves first the restoration of the normal moisture level in the boardafter the removal of the board from the press; This normal moisturelevel runs approximately 6 percent and is that amount of moistureconsidered necessary in a fully conditioned structural board. The boardmay then be trimmed by saws in order to remove rough edges. Followingthis the board may be sized or tempered. The tempering comprises thesubmersion of the board in drying oils followed by baking so as toproduce a hard, dense board having higher strength.

The total process including the many steps set forth above is commonlyreferred to as the wet process for hard board manufacture. There arenumerous modifications that may be successfully applied. One of the moreim portant variations is the dry process in which dry fibers arethoroughly mixed with dry additives, felted in dry form and hot-pressedwithout the addition of any appreciable moisture. An alternative processwhich may be followed involves coating the wet fibers with a syntheticresin binder, drying the fibers rapidly to prevent polymerization of theresin, dry-felting the fibers, and then subjecting the felt to hotpressing. Another variation is a combination of the wet and dryprocesses which comprises the preparation of a felt by the wet process,drying of the felt, and finally pressing the dry felt at elevatedtemperatures and pressures. In this process the ventilating screen isnot used and the board produced has a smooth surface onboth sides. Allof the methods described are applicable in carrying out the presentinvention.

Structural board made from straw can be produced as outlined in theabove methods but has the undesirable property of extreme susceptibilityto moisture. As a result this disadvantage is usually compensated for bythe incorporation of relatively large quantities of binders andwater-proofing agents which negates the advantage of the low cost fibersused. Another disadvantage of straw, grass, hay, and cereal fibers asraw materials is the expense accompanying the collection andtransportation of such materials to a central processing plant.

Among the objects of the present invention is the utilization of asubstantially useless fibrous material in the production of a structuralboard having certain improved properties over those of presently madecommercial structural boards.

Another object is to produce a highly desirable structural board frommaterial which requires less mechanical preparation .whose source iscentrally and conveniently located, which is available in substantialtonnage, and whose initial cost and processing cost is considerablybelow such costs of currently made structural boards.

Still another object of the present invention is to make a structuralboard, the major component of which is a partially digested vegetablefiber from straw, grass, cereals, and other vegetable fibers.

Other objects not specifically set forth will become apparent from thefollowing detailed description:

Generally, the invention comprises the production of a structural boardwhich contains as an essential starting ingredient a particular type ofmaterial referred to as rumen.

It has been found that straw, hay, grass, and other such vegetablesfiber raw material can be processed to yield an improved structuralboard having greatly increased resistance to water. A substantialportion of the processing of the aforementioned material may take placewithin the stomachs of ruminant animals, thereby providing aninexpensive system for concentrating large quantities of raw material ata large meatpacking establishment or near a group of suchestablishments. Comminuted straw, hay, grasses, or other ligno-cellulosevegetable fibers, or pith (e.g., corn cobs and peanut shells) may betreated with organisms normally found in the paunch, rennet, and/ orpeek of such ruminant'animals as cattle, sheep, calves,

' 4 and goats. The contents of the various stomachs of ruminants arecalled rumen and provide a rich source of desirable organisms.Infdefining rumen, the definition should not be extended to includemanure, as this material has been degraded to a point where it is nolonger suitable for utilization in board manufacture. As the rumencontains large quantities of hay, straw, and the like, and as it hasbeen ground and digested by the animal to the proper degree, ittherefore provides excellent fibrous material for the manufacture ofstructural board. Further, the rumen obtained from slaughtered animalscontains undigested comminuted grains which in the present processproduce starch suitable as one of the binders. Rumen also differs frommanure in that it provides no objectionable odor in the final board whenprocessed according to the present invention.

The general analysis of rumen as obtained from the ruminant animal is asfollows:

Percent Fat 2 Protein 5 Fiber 10 Water 83 The identity of all thecountless micro-organisms found in rumen has not been fullyaccomplished, but numerous species have been identified. Among theidentifiable species are:

Although laboratory cultures of such organisms can be utilized in thepresent invention, the expense of their culture and attainment of thedesired concentration is prohibitive. On the other hand, the naturalrumen, obtained as a waste product in meat packing operations, containsa rich source of such organisms in amounts which approach 10 percent ofthe total insoluble matter. As can be readily seen, the rumen not onlyis a source of excellent fibrous raw material but is also a source ofthe micro-organisms which function to produce a superior structuralboard.

In the practice of the present invention several different proceduresmay be followed, all of which make full utilization of the rumenmicro-organisms. In one form of the procedures the rumen in itsnaturally occurring state may be removed from the paunch, peck, orrennet of animals and used alone or with hinder or chemical additives inthe production of a structural board. The rumen used in this manner maybe in various stages of fermentation. This fermentation which occurswithin the animals due to the presence of the micro-organisms may alsooccur following the removal of the rumen from the animals. When theaction of the micro-organisms takes place upon removal from the animals,the pH of the rumen drops rapidly from 7 to approximately 5, where itremains constant. Further decomposition will occur if themicro-organisms are allowed to act over a substantial period of time. Ithas been found that rumen removed from the animals paunch and placed inpiles or suitable containers still function satisfactorily upon standingfor 30 days. Similar samples were allowed to stand over six months andupon testing appeared to have fermented to a point where a chemicalbreakdown of the fibers was present and the fibers had little, if any,strength left. In view of this, it is preferred to use rumen as obtainedfrom the animals or fermented stock which is under 40 days of age. I v

Another procedure has been found satisfactory wherein the rumen is mixedwith other suitable fibrous stocks obtained from wood, grass," hay,straw, paper, cobs, peanut shells, and the like. When rumen isused inthis manner it inoculates the stock and causes fermentation whicheventually produces a raw material suitable for the purposes. Inutilizing the inoculation procedure it is preferred that the inoculatedmaterial be subjected to fermentation for a period of from 24 hours toone week. In this procedure as in the aforementioned procedure themicro-organisms cause fermentation of the entire material and the pHdrops from 7 to approximately 5 and thereafter remains constant. Theaction by the microorganisms may be stimulated by the addition ofnitrogen or phosphorous compounds.

Additional procedures which may be followed include the mixing of rumenwith other comminuted fodder materials such as grass, hay, straw, canes,and so forth. The mixture is allowed to stand for a sufficient time toallow digestion and fermentation by the action of the micro-organisms.In a procedure such as this it may be necessary to add nutrients foroptimum activity of the micro-organisms. Other suitable fibrous stockssuch as that obtained from wood, paper, cobs, peanut shells, and thelike may also be added.

Upon obtaining the fermented stock by one of the procedures set forthabove, the stock may then be further refined by conventional mechanicalgrinding, followed by autoclaving sufficient to retard the fermentationand partially hydrolyze cereal grains and any other feed stuff present.In autoclaving it is preferred to utilize a time period of from 3 to 15minutes and a steam pressure of approximately 60 pounds. The autoclavingtime may be reduced Wherehigher pressures are utilized, or may beincreased under lower pressures dependent upon the circumstances. Thisautoclaving or cooking step completely eradicates the characteristicrumen odor and yields a product having the pleasant odor of ordinary wethay. The cooking also acceleratesthe solution of undesirable componentsso that they are easily drained off, thereby producing at the feltingstage a much more freely flowing stock. As a result, the felting time isconsiderably reduced.

The cooking or autoclaving step is not essential for the production of asatisfactory board from rumen. It has been found that a board containingmany highly desirable properties may be made according to conventionalpractices excluding the cooking. Cooking is necessary when wood chips,straw, paper, etc., are added as these materials are comparatively hardand are composed of bonded fibers. It is necessary to release the fibersand soften them in order that they may be properly felted. Whenutilizing rumen, the fibers present have been acted upon sufliciently bythe chewing action and digestive system of the ruminant so that feltingmay be satisfactorily accomplished without cooking. It is preferred,however, to cook, inasmuch as it simplifies the remaining steps. Wherecooking is utilized it is normally carried out in a closed vessel, thedesirable temperature range being approximately 200 to 300 F. and thetime required as high as one hour.

No comminuting or grinding is necessary prior to cooking rumen or priorto any other step utilized to properly condition the material. Due tothe grinding imparted by the ruminants teeth and the action of theruminants digestive juices on the constituents of rumen, the fiberbundles present are comparatively short and the material is in a highlycomminuted form when removed from the animal. This particular conditionof the stock materially cuts down the processing necessary to produce adesirable structural board. However, subjecting the starting material tofurther mechanical refining does aid in the appearance of the finishedboard.

" It has also been found that where the cooking step is utilized, theaddition of sufficient alkaline reacting material is helpful. i Thereason for this is that it has been found advantageous to adjust thestock to an approximate neutrality (pH 7.0' to 7.5). A neutral stock isnot absolutely necessary but itdoes facilitate the addi tionofresins andother binders, if desired, when these tendto precipitate under acidicconditions. Similarly, other additives may beincorporated during thecooking step in order to produce various desired degrees of hydrolysis,deodorization, bleaching, and so forth. Such additives are well knownand the desirability of making use ofthem depends on the particular typeof structural board desired.

Chemical treatment as normally practiced in commercial production of astructural board is not necessary where rumen is used as the majorcomponent in the stock. Generally, chemical treatment is utilizedprimarily tobring about the reduction of the raw material to fibers orfiber bundles. Rumen contains material in its fibrous state due to thereducing action brought about by grinding between the ruminants teethand by its digestive juices. The initial fibrous condition of rumenmaterially aids in'reducingthe cost of processing involved in themanufacture of a structural board.

The stock, either cooked or raw, may be subjected to a further refiningstep. If the stock has been cooked it may subsequently be mechanicallyrefined with or without cooling. With a cooked stock wherein thefermentation is arrested, the stock may be stored for future use if sodesired. On theother hand, where the fermentation is still in an activestate, the material should be subjected to refining and subsequentoperations within a reasonable time. The refining of the fibers isreadily achieved by passing the stock through a Bauer mill which hasbeen set to a clearance of from 2 to 50 thousandths of an inch,depending upon the fiber size desired. As the slurry of rumen pulp comesfrom the mill it is mixed, if desired, with other refined'stocks such asthose obtained from sawdust chips, scrap wood, paper, poultry feathers,scrap leather, and so forth. While the use of a Bauer mill is preferred,it has been found that satisfactory results are also obtained when aJordan or a Hollander paper pulp heater is used. In'instances where thestock contains a high percentage of hard material such as gravel, metal,minerals,- or incompletely refined cobs, shells, and so forth, itshould, be mildly agitated so as to suspend the fibers and to allow theheavy particles to sink. The fibers may then be floated off andintroduced into the Bauer mill for further processing. In. instanceswhere there is a very high fat content it is advisable to allow thewashed refined. stock tosettle, thereby permitting the removalof the fatby skimming.

While it is preferred that the rumen stock be refined prior to felting,it is nevertheless not essential. The rumen stock in'its natural formcan be said to be in a refined state due to the grinding and digestiveaction which has occurred. The only necessary step prior to felting isthe forming of a slurry. The comparatively short fiber bundles presentand the comparative freedom of these bundles allows the ready formationof a slurry suitable for felting. Where refining is practiced, a moreuniform board is obtained but in many instances such uniformity may notjustify the use of the special treatment.

The refined pulped slurry, with or without other fibrous stocks, is'then pumped to and mixed in a stock chest Where other additives may beincorporated accompanied by adequate agitation. Atthis point binders, ifdesired, may alsobe incorporated. Well-known binders such as phenolic.resins, casein, animal glue, and so forth, produce satisfactory results.At this point" it is also desirable to incorporate additives known toimpart improved moisture resistance. Such additives are alkalinesilicates, metal resinates, fats, waxes, and petroleum waxes.

The pulp slurry, plus the desired additives, is then allowed to flowonto a screenwhere the water drains off, producing a felt of the desiredthickness and size. Normally, gravity draining is all that isnecessaryand is preferred. In order to remove more free water, the feltis then given a cold pressingas by squeezing between rolls. Coldpressing is not essential but is considered desirable as it saves steamconsumption in the hot press. The hot pressing is preferably carried outat temperatures of from 250 to 400 F. and under pressures of from '100to 300 p.s.i. An alternative procedure consists in partially drying thecold pressed felt and ultimately subjecting the partially dried felt tohot pressing at higher temperatures and pressures. Hot pressing may becarried out in a number of stages to permit the escape of steam andother gases. The use of ventilating screens .on one or both sides of thefelt during pressing also facilitates the escapes of steam. Theresultant board coming from the press is bone dry. Normally it isdesirable to condition the board in a humidity room so as to increasethe moisture content to approximately 6 percent. Following conditioning,the board is trimmed to remove rough edges and then sized or tempered bysubmersion in a drying oil and baking in accordance with standardpractice. 7

An alternate procedure which may be followedand thereby alleviate thehumidity conditioning step is that in which a laminated board isproduced by the use of aqueous adhesive. Upon subjecting the laminatedboard to pressure for purposes of bonding the laminations, thehumidification of the laminations is carried out simultaneously, the dryboards gaining moisture from the aqueous adhesive.

The following examples are set forth as illustrative only of the presentinvention and are not to be consrued as limiting thereto: EXAMPLE I Thefollowing ingredients were utilized h 3100 grams rumen (wet) fermented11 days 54 gram sawdust e The rumen was beaten first and then subjectedto flotation whereby the fibers were floated and the undesirableconstituents were settled. The fibers and sawdust were then beaten in amechanical pulp beater for 7 minutes and a felt was made. The felt wasfirst cold-pressed to remove excess liquid, and then hot-pressed on ascreen at 365 B, using the following cycle: (1) to 100 p.s.i. in 3minutes (2) 100 to 200 p.s.i. in 1 minute (3) Held under 200 p.s.i. for12 minutes EXAMPLE n The following ingredients were utilized:

60% paunch stock (rumen aged 3 days) chrome savings 10% waste paper 10%chicken feathers 10% peanut shells 1600 grams of stock was diluted with3500 grams of water which resulted approximately in a 4 percent solidsslurry. The mixture was beaten in a Hollander beater until the desiredreduction of the paper shavings, feathers, and shells was accomplished.The refined stock was then felted in a felting box on a 30 mesh screen.Following felting, the wet felt was removed and hot-pressed on a screenat 200 p.s.i. within the temperature range of 380f-39 0 F. The resultingboard was room COHdi-r tioned for 24 hours, after which it washumidified at a 65 percent relative humidity for. 24 hours.

The properties of a board prepared in this manner are listedinTableL'EXAMPLE III The followi ng ingredients were utilized: V 60% wet rumen(dry basis) fermented 3 days 10% chrome shavings 10% waste paper 10%feathers 10% peanut shells EXAMPLE IV Composite stock of the samecomposition as th: t shown in Example HI, with the exception that theperiod of fermentation of the rumen was carried out for 34 days and therumen was rolled to crush any cereal grains present, was treated with 3percent of phenolic resin of a 10 percent solution and thoroughly mixed.The resin was precipitated on the fibers by lowering the pH toapproximately 6.0 with zinc chloride. The slurry was then felted,cold-pressed, and then hot-pressed on a screen at 375 F. and 200 p.s.i.for 20 minutes.

The properties of such a board are shown in Table I.

EXAMPLE V Composite stock of the same composition as that shown inExample 11, with the exception that the period of fermentation of therumen was carried out for 3 days, was treated with 1 /2 percent ofphenolic resin prior to felting. The pH of the refined stock wasadjusted to a pH of approximately 7.5 to 8 with sodium bicarbonate. Tothe adjusted solution was added a water solution of the resin. Theslurry was then thoroughly mixed and the resin was precipitated on thefibers with zinc chloride. The final pH was adjusted to approximately6.0-6.5. The stock was then felted, after which it was hot-pressed atp.s.i. for 20 minutes under temperature conditions within the range of380390 F. The formed board was then room conditioned and humidified asset forth above.

The resultant properties are listed in Table I.

EXAMPLE VI Composite stock of the same composition as that shown inExample II, with the exception that the period of fermentation of therumen was carried out for 3 days, was treated with 3 percent of phenolicresin prior to felting. The pH of the slurry was controlled in the samemanner as set forth in Example V and the binder precipitated as setforth therein. The stock was then felted and hot-pressed at 100 p.s.i.for 20 minutes under a temperature within the range of 380390 F. Theresultant board was then room conditioned and humidified as set forthabove.

The resultant properties of such a board are shown in Table I.

The weight of the specimens set forth in Table I is expressed in poundsper square foot. The thicknesswas measured in inches, and the maximumloads were determined by cross-bending specimens 3 inches. wide andusirg a 4-inch span. The modulus of rupture is expressed in pounds persquare inch. The last two values in Table I labeled Percent weightincrease and Percent thickness increase were compiled by measuring thepercent weight increase caused by the absorption of water in eachspecimen and the percent thickness increase caused by the absorption ofwater in each specimen. In both instances the water-soaking wasmaintained over a period of 24 hours. a

As can be seen from Table I, the properties of boards prepared as setforth in the examples are excellent. The maximum loads which such boardssustain per unit of Weight compare favorably with those of structuralboards commercially known. The modulus of rupture shown by these boardsalso compares favorably. The boards so formed are certainly equivalent,if not superior, to currently known commercial boards.

The boards produced as described provide anadvantage in that they createa use for material heretofore considered absolutely worthless. Not onlyhas this material been considered Worthless but its disposal has been aconstant problem in the packing industry. Many advantages of the rumenboard have been shown but it should be pointed out that an even greateradvantage is also present. The water-resistant qualities of boards madefrom rumen is clearly established by the figures of Table I. As can beseen from this table, the percent weight increase caused by waterabsorption is comparatively small, and the percent thickness increase ispractically negligible. Structural boards made of straw, etc., byconventional procedures are highly absorbent and, due to this property,havebeen in many cases unsatisfactory for many purposes where contactwith moisture is necessary. As a result, the conventional boards must bewaterproofed with expensive waterproofing materials so as to produce anall-purpose board. The wide use of structural board for buildingpurposes has dictated the requirement that the structural boards usedhave such properties as to withstand weather conditions with whichbuilding materials are normally subjected. Not only has the use of largeamounts of waterproofing increased the cost of structural boards, but ithas also increased the weight thereof, and, as a result, has limitedsomewhat its utility. As can be seen from Table I, structural boardsmade principally from rumen display a high natural water-resistantproperty, and it therefore follows that the amount of waterproofingmaterial necessary to provide a structural board even more waterrepellent is greatly reduced. Due to this feature the cost of the boardis reduced, the extent of treatment involved in manufacture is greatlyreduced, and a lighter-weight board having all of the necessary anddesirable properties of structural board is formed.

It should also be noted that little, if any, binding agents arenecessary in the production of a structural board in which the principalingredient is rumen. Example I sets forth the production of a board inwhich the only ingredients utilized are wet rumen and sawdust. As can beseen from the properties of this board, the absence of a binding agentdoes not materially alter the properties of the finished product. A verysubstantial and desirable board can be made without the use ofadditional agents, such as binding agents. This represents anotherfeature of a board made from rumen whereby the expense and labornecessary to produce such aboard is materially altered.

The highly desirable properties present in structural boards made fromrumen cannot be readily explained. On the basis of the knowledge gainedby the hardboard industry from years of experimentation it has generallybeen conceded that the length of fibers obtained from 10 the variousstocks has much to do with the ultimate attainment of desirableproperties in the finished board; It has generally been considered thata very desirable stock is that which produces comparatively long fibersand fiberbundles. This has been believed to be necessary in that thestrength of the board is substantially dependent on the intertwining orinterlacing of the fibers. Rumen, on the other hand, is made up ofcomparatively short fiber bundles and, therefore, by accepted standardswould not normally be considered a proper source material.

Along with the short fiber characteristic of rumen there are otherfactors which would not ordinarily be considered capable of lendingthemselves advantageously to the formation of a highly desirable andimproved board. The source material Which goes into the make-up of rumenconsists of such things as grass, hay, oats, etc. Such material containsmany components which would normally be considered harmful to the endresult of structural board manufacture. Hard joints on the stems ofstraw where the kernels are attached would normally represent a problemin board manufacture, yet seems to have little effect when present inrumen. The diet of the ruminant varies throughout the year and the rumencollected. is non-uniform when analyzed from time to time. Yet the.non-uniformity does not appear harmful to the resultant properties ofarumen structural board. The corn which appears in the rumen at certaintimes in the year seems to have little adverse effect. Fat isquite'often found to be present and would normally be consideredextremely undesirable. However, small amounts of fat do not appear tohave a detrimental effect on rumen boards. While the properties of theboards may vary slightly, the range of variance is only slight and theoverall range of properties is well within or above the ranges ofacceptability. Such slight variances cannot clearly be traced to thenon-uniformity of the stock and, therefore, can be explained adequatelyas due to production procedures. Such variances are highly prevalent andconstantly present in the industry even where standardized stocks areutilized.

Rumen boards have shown strength properties which are comparable to orare better than those of commercial hardboards made today. Yet whenusing rumen as an essential ingredient the procedure followed inproducing a board may be materially altered. As stated above,comminution, cooking, and refining are not absolutely necessary. In manyinstances, dependent on the composition of the stock, there is no needfor them. Boards made of rumen are pressed at pressures ranging from to300 p.s.i. in contrast to 500 to 750 p.s.i. for conventional hard boardmanufacture. With this difference in mind it is readily apparent that amaterial savings in equipment, time, and operational costs may berealized, while a superior board is the resultant product.

In the use of phenolic resin as a binder it has been found that from 1to 5 percent resin gives desirable results. The resin may be added as anaqueous solution at a pH above 7.0 and then precipitated with theaddition of sufiicient acid to bring the pH down to below 6.5. It may bedesirable to utilize certain acids which not only precipitate the binderbut also act on the fibers. Such an acid, for example, is oxalic acidwhich also serves as a bleaching agent. Other binders give satisfactoryresults also. Among these are starch and animal glue. When starch itused it may be added directly in its pure form or may be added in situby comminution of amylaceous cereal grains present in the rumen.Normally, from 1 to 10 percent starch has been found desirable. Withrespect to animal glue it has also been found that the desirablepercentage range is approximately 1 to 10 percent. The glue may be addedand then precipitated with formaldehyde or the like. Another methodconsists in adding from 1 to 10* percent 11 collagenous material whichis in pulp form and which has been previously'cured so as to yieldanimal glue with or without formaldehyde when heat or pressure isapplied.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. In the production of a structural board, wherein rumen is utilized asa major ingredient thereof, the method which comprises: forming a slurryof stock, said stock including as a major ingredient thereof rumen;felting the said stock whereby a mat of fiber bundles is formed, saidmat being suitable for compressing; and thereafter pressing said feltedmat under pressures not exceeding 300 pounds per square inch.

2. In the production of a structural board, wherein rumen is utilized asa major ingredient thereof, the method which comprises: forming a slurryof stock, said stock including as a major ingredient thereof rumen,felting the said stock whereby a mat of fiber bundles is formed, saidmat being suitable for compressing; and thereafter hot pressing saidfelted mat under a pressure within the range of from 100-300 pounds persquare inch.

3. In the productionof a structural board, wherein rumen is utilized asa major ingredient thereof, the method which comprises: forming a slurryof stock, said stock including as a major ingredient thereof rumen,felting the said stock whereby a mat of fiber bundles is formed, saidmat being suitable for compressing; cold-pressing said felted mat toremove a substantial quantity of liquid therefrom and thereafterhot-pressing said cold-pressed mat under pressures not exceeding 300pounds per square inch.

4. In the production of a structural board, wherein rumen is utilized asa major ingredient thereof, the method which comprises: forming a slurryof fibrous stock having rumen incorporated therein, refining said slurryand thereby removing unwanted foreign material therefrom, treating saidrefined slurry with an alkali to adjust the pH of said slurry above 7.0;adding to said treated slurry a small amount of phenolic resin causingsaid resin to precipitate upon said fibrous stock by reducing the pH ofsaid slurry below the value of 6.5; felting said fibrous stock to form amat suitable for compressing and thereafter pressing at a pressurewithin the range of from 100-300 pounds per square inch and conditioningthe fibrous stock whereby a commercial hard board having desirablestrength and moisture resistant properties is formed.

5. In the production of a structural board wherein rumen is utilized asa major ingredient thereof, the method which comprises: forming a slurryof fibrous stock having rumen incorporated therein; refining said slurryand thereby removing unwanted foreign material therefrom; adding starchto said slurry in sufficient amounts to act as a binder therein; feltingsaid slurry to form a mat suitable for compressing and thereafterpressing at a pressure not exceeding 300 pounds per square inch andconditioning the material whereby a commercial hard board havingdesirable strength and moisture resistant properties is formed.

6. In the production of a structural board wherein rumen is utilized asa major ingredient thereof, the method which comprises: forming a slurryof fibrous stock having rumen incorporated therein; refining said slurryand thereby removing unwanted foreign material therefrom; adding curedcollagenous material in pulp form to said slurry; felting said slurry toform a mat suitable for compressing and thereafter pressing at apressure not-exceeding 300 pounds per square inch and conditioning Saidmatwhereby a commercial hard board having desirable strength andmoisture resistance properties is formed/,1

.7.. In the productionof a structural board wherein r'umenis utilized asamajor ingredient thereof, the method which comprises: forming a slurryof fibrous stock having rumen incorporated therein; refining said slurryand thereby removing unwanted foreign material therefrom; adding acomparatively small quantity of animal'glue to'said slurry followed bythe addition of formaldehyde torprecipitate said glue on the fibers;felting the slurry to form a mat suitable for compressing and thereafterpressing at a pressure not exceeding 300 pounds per square inchand-conditioning said mat whereby a commercial hard board havingdesirable strength and moisture resistance properties is formed,

8. In the production of a structural board wherein rumen is utilized 'asa major ingredient thereof, the method which comprises: forming a slurryof fibrous stock which contains as ingredients thereof rumen and a smallportion of comminuted amylaceous cereal grains; felting the said stockwhereby a mat of fiber bundles is formed, said. mat being suitable forcompressing; and thereafter pressing said felted mat under pressures notexceeding 300 pounds per square inch.

9. In the production of a structural board wherein rumen is utilized asa major ingredient thereof, the method'Which-consists of forming aslurry of fibrous stock which contains rumen as an ingredient thereof;refining said slurry and thereby removing foreign mattertherefromyintroducing into said stock binders and other chemicalswhereby the resultant properties of the finished board are controlled;felting said stock to form a mat suitable for compressing and thereafterpressing at a pressure not exceeding 300 pounds per square inch andconditioning said stock whereby a commercial hard board havingdesirable-strength and moisture resistance properties is formed.

10. A method of producing a structural board which comprises fermentingrumen removed from the paunch of cattle to a pH of 5 and for a periodnot to exceed 40 days, forming an aqueous slurry containing said rumenas a principal ingredient, felting said slurry whereby a fibrous mat isformed, and hot pressing the fibrous mat at a pressure not exceeding 300pounds per square inch.

- 11. A method of producing a structural board comprising fermenting amixture of cattle rumen and other fibrous material to a pH of 5, saidmixture containing said cattle rumen as a major ingredient thereof,forming an aqueous slurry of said mixture, felting said slurry whereby.a fibrous mat is formed, and hot pressing the I fibrous mat at apressure not exceeding 300 pounds per square inch.

12. The product of the process as described in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN THE PRODUCTION OF A STRUCTURE BOARD, WHEREIN RUMEN IS UTILIZED ASA MAJOR INGREDIENT THEREOF, THE METHOD WHICH COMPRISES: FORMING A SLURRYOF STOCK, SAID STOCK INCLUDING AS A MAJOR INGREDIENT THEREOF RUMEN;FELTING THE SAID STOCK WHEREBY A MAT OF FIBER BUNDLES IS FORMED, SAIDMAT BEING SUITABLE FOR COMPRESSING; AND THEREAFTER PRESSING SAID FELTEDMAT UNDER PRESSURES NOT EXCEEDING 300 POUNDS PER SQUARE INCH.